It has previously been proposed to alter the rate and character of hair growth by applying to the skin inhibitors of certain enzymes such as inhibitors of 5-alpha-reductase or of ornithine decarboxylase, or such antiandrogen materials as cytoplasmic androgen receptor binding agents, as described in U.S. Pat. Nos. 4,720,489 and 4,885,289. Moreover, it has been theorized that other enzymes, including gamma-glutamyl transpeptidase, are involved in various stages of hair follicle formation or of hair growth, but the relation between the various enzymes and the reactions which they control, as well as their effect upon each other and upon hair growth, has not been fully understood, as appears from Richards et al, Cancer Research, Vol. 42, 4143-4152 (1982); DeYoung et al, Cancer Research, Vol. 38, 3697-3701 (1978); and Chase, Physiolo. Zool., Vol. 24, 1-8 (1951).
It has now been found that the rate and character of mammalian (including human) hair growth, particularly androgen-stimulated hair growth, is altered by topical application to the skin of a composition containing an inhibitor of adenylosuccinate synthetase or of aspartate transcarbamylase.
Among the inhibitors of adenylosuccinate synthetase which may be used in the present invention are L-alanosine ([L-2-amino-3-(N-hydroxy, N-nitrosamino) propionic acid]), 6-mercaptopurine riboside 5'-phosphate, 8-aza guanosine monophosphate, 7-deaza-8-aza guanosine monophosphate, 2'-d guanosine monophosphate, .beta.-D-arabinosyl guanosine monophosphate and the like. Inhibitors of aspartate transcarbamylase include N-phosphonacety -L-aspartic acid (PALA), 2-[[(phosphonomethyl) thio]methyl] succinic acid, O-phosphonoacetyl-L-malic acid, halogenated phosphonoacetyldioic or halogenated phosphonoacetyl aminodioic acids as described in European Patent Application 8,834 A, and bromosuccinate, among others. Of these, L-alanosine and PALA are preferred. It should be noted that L-alanosine is metabolically activated to L-alanosyl-5-amino-4-imidazole carboxylic acid ribonucleotide, which is formed in vivo and which is the direct or proximate inhibitor of the enzyme adenylosuccinate synthetase. L-alanosine is thus an indirect inhibitor of the enzyme but is included within the term inhibitor for the purpose of the present invention.
The composition of the present invention contains, in addition to the inhibitor, a non-toxic dermatologically acceptable vehicle or carrier which is adapted to be spread upon the skin. The concentration of the inhibitor in the composition may be varied over a wide range up to a saturated solution, preferably from 0.1 to 20% by weight or even more; the reduction of hair growth increases as the amount of inhibitor applied increases per unit area of skin. The maximum amount effectively applied is limited only by the rate at which the inhibitor penetrates the skin. Generally, the effective amounts range from 10 to 2500 micrograms or more per square centimeter of skin.
The following specific examples are intended to illustrate more clearly the nature of the present invention without acting as a limitation upon its scope.